A website used to co-ordinate computer attacks on Sony and other big companies by members of Anonymous has itself come under assault in what security experts and veterans of the organisation see as evidence of a split within the hacking group.

The site, AnonOps.net, us­ually lists discussion groups for activities such as “denial-of-service” attacks, which flood targeted websites with meaningless traffic until they cannot be reached by the public.

But the site has been defaced with obscenities, and login names and internet addresses of more than 500 people alleged to have taken part in Anonymous activities have been posted on it.

Private security experts and veterans of the group said they believed the attack against the site was the result of a split in the leadership of Anonymous that could undermine the organisation’s effectiveness.

“Maybe this was due to happen. Anonymous has been surprisingly functional over the last months. It wouldn’t last,” said Mikko Hypponen, chief security officer at Finland’s F-Secure, an anti-virus company.

After gaining prominence by targeting the Church of Scientology in 2008, Anonymous has gone on to target government websites in pre-revolution Tunisia, perceived opponents of whistle-blowing site WikiLeaks and recording industry groups it accused of heavy-handed tac­tics in combating digital piracy.

The group is amorphous by design, and there are other online gathering places for those who want to participate in its activities. But many of the technical resources of Anonymous were in the hands of a dozen or so “administrators” who controlled computers hosting online chats, said Gabriella Coleman, a New York University professor studying the group.

Some of those purported administrators said on other sites and on Twitter that a rebellion was taking place within Anonymous.

“We are profoundly sorry for this drama, and we can’t give you an estimate on when service will resume normally,” said a message posted over the weekend on website AnonOps.in and signed by five people calling themselves “the ‘Old’ AnonOps netstaff ”.

Some security professionals, who say they are working in a voluntary capacity, have forwarded internet chat logs and internet addresses of alleged Anonymous members to the Federal Bureau of Investigation. These experts said they had fielded questions from the FBI about the alleged rift and about possible leaders on both sides.

The FBI is investigating whether Anonymous members were involved in a massive data breach at Sony’s online gaming networks. The FBI and Sony declined to comment.

Sony on Tuesday apologised again for the ongoing unavailability of its Playstation Network, saying it would be “at least a few more days” before its digital entertainment services were back online.

In messages on their new site, the “Old” AnonOps managers blamed a hacker named Ryan for revealing data on group members. In retaliation, they published what they said was his full name and address. Att­empts by the Financial Times to reach Ryan by telephone and Skype have failed.

Someone named Ryan told the online publication Thinq.co.uk he was acting because the old group had become too centralised and hungry for media attention.